Teeny janitors attack Gulf spill, then vanish

February 9, 2011

Robert Krulwich

Illustration by Adam Cole

Last spring, a website called Helium reported breathlessly that BP's release of methane gas into the Gulf of Mexico would not only poison the water, the fish and the neighborhood, but it also very possibly could trigger "a world-killing event" — perhaps releasing a "mammoth undersea methane bubble" that would destroy much of life on Earth.

Nobody gulped. Yes, BP's oil and methane leak was gigantic. Dangerous amounts of methane were concentrating in Gulf waters. But "world-killing"? That silly story was largely ignored. Strangely, so was the story that broke a few weeks ago, which was just as surprising, just as improbable, just as astonishing — but this one was true.

Where's The Gas?

Last June, oceanography professor John Kessler of Texas A&M University visited the accident site and found methane concentrations below the surface that were, "on average about 100,000 times greater than background [usual]." He told Living On Earth, "We even saw a few locations that were starting to push the limits of a million times above background."

That's a lot of methane. Which is not a good thing. Because methane is a potent greenhouse gas, more potent than CO2. What's more, it's lurking everywhere, not just in the Gulf, but under the Arctic Ocean, the Black Sea. Should large quantities escape into the atmosphere, that would make our warming problems even worse.

And more concerning, as the Earth warms, what if methane trapped under ice loosens and rises to the surface? Alaskans see this. Their permafrost is softening. Often the methane is just below, as you can see here, when this gang from the University of Alaska pokes a hole in some ice and sets the gas on fire. It doesn't end well.

What can we do about the methane threat? Is there a way to get rid of the gas before it escapes? How much time do we have? Professor Kessler, reporters, almost everybody predicted that the Gulf methane (like the Alaska methane) would hang ominously below the surface for years, "like a massive planetary fart" (in the memorable phrase from one of my favorite bloggers, Ed Yong).

But guess what happened?

In August, Kessler sailed out on the NOAA ship Pisces to check on the gas plume. Three months had passed. 120 days. He looked. He looked again. The gas was gone.

The enormous concentrations he'd seen in June had disappeared.

Where'd the gas go?

They Came, They Cleaned, They Went

Kessler was dumbfounded. But he now has an explanation. The gas, he thinks, was eaten.

There are ocean bacteria called "methanotrophs." They hang around, usually in smallish numbers, but because they love chewing on methane, when the accident happened, Kessler figures they got their chance to be fruitful and multiply — and multiply they did.

We should be careful. Kessler didn't witness the feast. He came back too late, so all he saw was the missing methane and a lower than normal amount of oxygen.

Kessler's new paper, co-authored with David Valentine, points out that many methane eaters use oxygen to break down the gas, so, says blogger Ed Yong:

Kessler reasoned that the microbes had done away with the methane. He even found the bacteria in question. In September, Kessler recovered several species of methane-eating bacteria from seven different sites. In some areas, these [methanotroph] specialists made up a third of the local bacteria. Back in June, the methane-eaters were nowhere to be found ...

If Kessler's theory is right, this is very, very good news. Even if the world gets warmer, all of that methane gathered under the oceans, trapped under ice, may never make it to the surface and into our atmosphere. Instead, it could become lunch for the methanotrophs.

Ed Yong quotes a string of leading oceanographers who say Kessler's paper is surprising and persuasive. "[It's] likely to become a classic reference," says Richard Camilli of Woods Hole Oceanographic Institution.

But not everybody was celebrating. NPR's excellent Richard Harris found an oceanographer at Florida State University who says these ocean bugs don't usually eat so fast. Maybe, just maybe, says Ian MacDonald, a big ocean current just swept through the Gulf and carried the methane off to the Atlantic Ocean?

Maybe. But maybe this is just plain old good news, and a summer-long disaster has just taught us a happy secret about Mother Nature: that when bad stuff happens, She still has little friends in low places who will clean up our messes. Thank you, methanotrophs. Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.